package com.guoranhao.tool.utils;

import java.io.IOException;
import java.io.InputStream;

public class FileValidator {

    /**
     * byte数组转换成16进制字符串
     *
     * @param src
     * @return
     */
    public static String bytesToHexString(byte[] src) {
        StringBuilder stringBuilder = new StringBuilder();
        if (src == null || src.length <= 0) {
            return null;
        }
        for (int i = 0; i < src.length; i++) {
            int v = src[i] & 0xFF;
            String hv = Integer.toHexString(v);
            if (hv.length() < 2) {
                stringBuilder.append(0);
            }
            stringBuilder.append(hv);
        }
        return stringBuilder.toString();
    }

    /**
     * 根据文件流读取图片文件真实类型
     *
     * @param is
     * @return
     */
    public static String getTypeByStream(InputStream is) {
        byte[] b = new byte[4];
        try {
            is.read(b, 0, b.length);
        } catch (IOException e) {
            e.printStackTrace();
        }
        String type = bytesToHexString(b).toUpperCase();
        if (type.contains("FFD8FF")) {
            return "jpg";
        } else if (type.contains("89504E47")) {
            return "png";
        } else if (type.contains("47494638")) {
            return "gif";
        } else if (type.contains("49492A00")) {
            return "tif";
        } else if (type.contains("424D")) {
            return "bmp";
        }
        return "png";
    }

}
